/*
Test case for collision/jerking issue.
*/

#include "test.h"

#include <vector>
#include <iostream>

class Skier : public Test
{
public:
    Skier()
    {
        b2Body* ground = NULL;
        {
            b2BodyDef bd;
            ground = m_world->CreateBody(&bd);

            float const PlatformWidth = 8.0f;

            /*
            First angle is from the horizontal and should be negative for a downward slope.
            Second angle is relative to the preceding slope, and should be positive, creating a kind of
            loose 'Z'-shape from the 3 edges.
            If A1 = -10, then A2 <= ~1.5 will result in the collision glitch.
            If A1 = -30, then A2 <= ~10.0 will result in the glitch.
            */
            float const Angle1Degrees = -30.0f;
            float const Angle2Degrees = 10.0f;

            /*
            The larger the value of SlopeLength, the less likely the glitch will show up.
            */
            float const SlopeLength = 2.0f;

            float const SurfaceFriction = 0.2f;

            // Convert to radians
            float const Slope1Incline = -Angle1Degrees * b2_pi / 180.0f;
            float const Slope2Incline = Slope1Incline - Angle2Degrees * b2_pi / 180.0f;
            //

            m_platform_width = PlatformWidth;

            // Horizontal platform
            b2Vec2 v1(-PlatformWidth, 0.0f);
            b2Vec2 v2(0.0f, 0.0f);
            b2Vec2 v3(SlopeLength * cosf(Slope1Incline), -SlopeLength * sinf(Slope1Incline));
            b2Vec2 v4(v3.x + SlopeLength * cosf(Slope2Incline), v3.y - SlopeLength * sinf(Slope2Incline));
            b2Vec2 v5(v4.x, v4.y - 1.0f);

            b2Vec2 vertices[5] = {v5, v4, v3, v2, v1};

            b2ChainShape shape;
            shape.CreateLoop(vertices, 5);
            b2FixtureDef fd;
            fd.shape    = &shape;
            fd.density  = 0.0f;
            fd.friction = SurfaceFriction;

            ground->CreateFixture(&fd);
        }

        {
            float const BodyWidth  = 1.0f;
            float const BodyHeight = 2.5f;
            float const SkiLength  = 3.0f;

            /*
            Larger values for this seem to alleviate the issue to some extent.
            */
            float const SkiThickness = 0.3f;

            float const SkiFriction    = 0.0f;
            float const SkiRestitution = 0.15f;

            b2BodyDef bd;
            bd.type = b2_dynamicBody;

            float initial_y = BodyHeight / 2 + SkiThickness;
            bd.position.Set(-m_platform_width / 2, initial_y);

            b2Body* skier = m_world->CreateBody(&bd);

            b2PolygonShape ski;
            b2Vec2 verts[4];
            verts[0].Set(-SkiLength / 2 - SkiThickness, -BodyHeight / 2);
            verts[1].Set(-SkiLength / 2, -BodyHeight / 2 - SkiThickness);
            verts[2].Set(SkiLength / 2, -BodyHeight / 2 - SkiThickness);
            verts[3].Set(SkiLength / 2 + SkiThickness, -BodyHeight / 2);
            ski.Set(verts, 4);

            b2FixtureDef fd;
            fd.density = 1.0f;

            fd.friction    = SkiFriction;
            fd.restitution = SkiRestitution;

            fd.shape = &ski;
            skier->CreateFixture(&fd);

            skier->SetLinearVelocity(b2Vec2(0.5f, 0.0f));

            m_skier = skier;
        }

        // g_camera.m_center = b2Vec2(m_platform_width / 2.0f, 0.0f);
        // g_camera.m_zoom = 0.4f;
        m_fixed_camera = true;
    }

    void Keyboard(int key) override
    {
        switch (key)
        {
        case GLFW_KEY_C:
            m_fixed_camera = !m_fixed_camera;
            if (m_fixed_camera)
            {
                //		g_camera.m_center = b2Vec2(m_platform_width / 2.0f, 0.0f);
            }
            break;
        }
    }

    void Step(Settings& settings) override
    {
        DrawString(5, m_textLine, "Keys: c = Camera fixed/tracking");

        if (!m_fixed_camera)
        {
            // g_camera.m_center = m_skier->GetPosition();
        }

        Test::Step(settings);
    }

    static Test* Create() { return new Skier; }

    b2Body* m_skier;
    float m_platform_width;
    bool m_fixed_camera;
};

static int testIndex = RegisterTest("Bugs", "Skier", Skier::Create);
